What happened
On 13 December 2013, a Boeing 757-256, registration G-ZAPX, was conducting a commercial passenger flight from London Gatwick to Freetown-Lungi Airport in Sierra Leone. While performing a VOR approach for Runway 30, the aircraft was positioned above the intended glidepath and traveling at an excessive speed.
After requesting descent clearance multiple times, the crew turned onto the final approach track with significant excess energy. To correct the profile, the pilot extended the landing gear at 185 kt and disconnected the autopilot. The crew utilized speed brakes, deploying them partially at 1,450 ft and fully at 1,000 ft, while attempting to manage a high rate of descent.
As the aircraft descended, the Enhanced Ground Proximity Warning System (EGPWS) triggered a "sink rate" alert at 500 ft, followed by a "pull up" warning at 350 ft. Despite these warnings and the unstable nature of the approach, the crew elected to continue to the runway. The aircraft touched down with the speed brake still deployed, having maintained a high rate of descent until reaching an altitude of approximately 150 ft.
The investigation
The AAIB investigation utilized data from the Quick Access Recorder (QAR) to reconstruct the flight profile. The investigation established that at 500 ft, the aircraft was traveling at 155 kt, which was 22 kt above the reference landing speed, and descending at approximately 1,900 feet per minute. The investigation also reviewed the crew's decision-making process regarding the decision to continue the landing despite the EGPWS alerts and the unstable approach parameters.
Findings
- The approach was unstable due to the aircraft being above the correct glidepath and exceeding the target approach speed.
- The crew attempted to regain the correct profile by using speed brakes and a high rate of descent, but failed to initiate a go-around.
- EGPWS "sink rate" and "pull up" alerts were triggered during the final stages of the approach.
Safety action
Following the incident, the operator updated its flight procedures. The pilot monitoring is now required to make a specific call at 500 ft radio altitude. If the approach is stable, the call "500 stable" is made; if the approach is deemed unstable, the pilot monitoring must call "500 Go-Around," requiring the pilot flying to execute the maneuver immediately.